Aeo light



Aug. 4, 1931. i T. W. CASE 1,816,825

AEO LIGHT Filed May 2s, .1927

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Patented Aug. 4, 1931 UNITEDSTATES ,PATENT omer THEODORE WILLARD CASE, F AUBURN, NEW YORK, ASSIGNOR TO CASE RESEARCH LABORATORY INCORPORATED, OF AUBURN, NEW YORK, A CORPGRATION 0F NEW I YORK AEO LIGHT Application led May 28,

This invention relates to certain new and useful improvements in sources of light for producing a photographic record of electrical variations corresponding to sound r, Wave variations and to the method of producing such sources of light and is a continuation in part of my prior application, Serial No. 719,098, tiled June th, 1924.

The main object of the invention resides w in the method ofproducing a source of light which varies instantaneously and accurately in accordance with variations in the electric current iiowing in a circuit connectedy across the electrodes of the lamp. n l

5 A further object contributing substantially to the above described lamp resides in the particular method of activating the cathode whereby a more e'ective and stable source of llight is produced for the purpose above dey scribed.

A further object resides in the production of a source of light which can be used for comparatively long periods of time without decrease in effectiveness.

Other objects and advantages relate to the details ofthe source of light and method of producing the same, all as will more fully appear from the following description taken in connection with the accompanying drawings, in which f The three iigures are sectional views of the source of light including more or less diagrammatic.illustrations ofthe method of producing the lamp and activating the electrodes thereof.v l

Generally speaking, the source of light includes a ybulb -1- containing a pair of spaced electrodes 2 and -3-. The anode `2 may be formedr of a nickel plate and a satisfactory size for the plate is 1 /lith of an'inch by 1/8th of aninch and .005 of an inch thick. n.

Thecathode 3 may be formed of a platinumwire .0023 of an inch by .011 of an inch and 3/4fths of an inch long. The cathode 3- is preferably in the form of an inverted U and this form seems to be important becausey the source'of light retains its eiiciency for longer periods kof time than when the cathode is straight, and this seems to result from the 1927. Serial N0. 195,129.

ly associated and a satisfactory condition isV found when the plate -2- is spaced approxilmately 3/16-ths of an inch from the filament or cathode -3-. The U-shaped cathode is attached at its ends to two leads -4- and -5- so that it may be used as a filament and may be heated by the passage of electric current therethrough.

The stem 6 of the bulb -1- projects upwardly a sufficient distance so as to surround the leads and all portions of the cathode -3- that are not coated as hereinafter described, so that only the portions of the cathode which have an oxide coating can glow.

This feature is found important if smooth reproduction is desired because it prevents the glow from running down any uncoated portion of the electrode when the light is modulated. A

The platinum strip which constitutes the basic portion of the cathode -3 is preferably twisted, and just before sealing the stem -6 into the shell of the bulb -1-,

the exposedportion of the platinum wire is l coated with calcium nitrate while a current of 2.9 amperes is flowing through the filament or platinum wire.

This forms a layer of calcium oxide -as a protection to the platinum wire. The current iowing through the platinum wire is then increased to 3.1 amperes and a heavy smooth layer of barium nitrate is coated upon the calcium oxide and the hot platinumiilament changes the barium nitrate to barium oxide. The stem carrying the leads and the platinum filament adapted to constitute the cathode 3.- 'v and also carrying the plate or anode -2- is sealed into the shell of thebulb -q-lfas rapidly as possible, preferably with a gas oxygen flame, as such a flame seems better than an Oxy-hydrogen ame because of the smaller amount of water evolved by the fires and the question of keeping moisture away from the coating of the cathode is important because it appears that under the influence of heat and moisture of the sealing flames, there is' a certain amount of hydroxides formed.

Preferably, a drying material, such as phosphorous-pentoxide is used in the blow tube to keep` moisture from the operators breath from entering the-tube or bulb. The tube or bulb is then sealed onto a vacuum pump, as for instance by pipe`7 and it is then ready for the process of evacuation and baking.

v The vacuum pump 'is started and an alternating current of one-half ampere is run through the filament or. cathode -3- for instance, as illustrated in Figure'l, the leads -4- and 5 being shown diagrammatically as connected to a generator -,8- of al-v ternating current.

- The tube is baked at 300 degrees centigrade for about one-half an hour, and then the temperature is raised to about 400 degrees centi'- grade, and the alternating current flowing through the cathode -3- to about 1 ampere. The temperature during the first half hour of baking is kept at about 300 degrees C. iny

order that the hydroxides may be decom! filament is brought up to a dull red. This feature of heating the cathode with its oxide coating to a dull red in a high' vacuum is of extreme importance in activating the coating on the platinum wire of the cathode -3-, and in the production of a cathode of unusual stability, and unusual effectiveness in the production 'of a constant and uniform light which will vary instantaneously and sharply in accordance with variations in anV electric circuit connected between the l.cathode 3F- and .the anode 2.

The anode -2-- is then connected in circuit with the cathode 4 3-, such circuit including an alternating current of about 1200 volts. As illustratedin Figure 2, this alteri a green glow comes from the filamentlor nating current may be evolved from a transformer -9- with two 10U-watt lights 10 in series with the primary windings.l VAt the same time a direct current of 'approximately 2.6 amperes is caused to fiow through the cathode -3-, as for instance by a circuit 'connected to the leads from the ends of the cathode, which circuit includes a source of direct current, as battery +11-.

This current is allowed to flow until the plate or anode -2- is red hot and the characteristic spectrum of the cathode coating material is produced, or in the case `of barium mitted to the tube -1- until the desired pressure is reached, at which time a glow will appear on both plate and filament. When such pressure is reached, the current is shifted from alternating current, as above described, to a direct current of about 350 volts with a resistance of about 10,000 ohms in ser1 f A diagrammatically illustrated in Figure 3,' the anode and-the cathode may be connected in circuit including the desired source of potential, as battery -12-, and the desired resistance -13-, the,positive terminal of the battery being attachedlto the plate and the negative terminal being attached to the filament.

This association of elements'will cause the filament to glow and if the entire exposed length of the filamentds not active, it maybe made so by increasing the voltage to about 450 volts for several minutes. The gas pressure is then adjusted to give the correct current reading, and a satisfactory reading is found to be between five to 10 milliamperes on 315 volts with 10,000 ohms in series.

The tube is then ready to be sealed ofi' and used.

The light of this invention is essentially a lcathode glow lamp in which a highly intense negative or cathode glow is concentrated about the cathode, and is separate from the anode glow at operating voltage, and at the gas pressure utilized, and it is this cathode glow that is photographed in the production of a sound record.

It is found, however, that when the light is operated the cathode or negative low includes a helium glow concentrated a out the negative electrode and outside of this helium glow there is a green halo which shows the presence of a barium glow in some form, probably either barium metal orbarium suboxide, and therefore, the light ofthis invention is not a pure gas discharge light, but shows a combination gas and metalspectrum. v

It is found that when strontium' is used instead of barium the resultant halo surrounding the gas glow is bluish.

Altho I refer barium oxide as the mater1al with w ich the cathode is to be coated, it is. found that other alkaline vearth oxides,

such as strontium, may be utilized, and a-ltho tube is filled, itis found that other inert gases, such as Argon, may be used and for the reason'that the particular features of the method here deemed to constitute invention do not relate tothe particular gas utilized, or the particular alkaline earth oxide utilized, except in preferred forms, I do not desire to restrict myself to the details of themethod or the device described, or the particular materials utilized, or their exact form, except where such details are specifically included in the claims hereto appended.

I claim: f

1. In the method of manufacturing a sourceI of light for producing'a photographic record of light wave variations corresponding to sound wave variations, the steps consisting in providing an electrode with an alkaline earth oxide coating, then heating the y electrode to a red heat while enclosed in a highly evacuated space, connecting said coated electrode in circuit with a second electrode positioned in said evacuated space and passing an alternating current through said circuit until the coated electrode showsthe characteristic spectrum of the. coating material.

2. In the method of v manufacturing a source of light for` producing a photographic record of light wave variations corresponding to sound wave variations, the steps consisting in providing an electrode with an electrode with an alkaline earth oxide coating, then heating the electrode to a red heat while enclosed in ahighly evacuated space, connecting said coated electrode in circuit with a second electrode positioned in said evacuated space and passing an electric current through said circuit until the characteristic spectrum of the coating material comes from the coated electrode and the other electrode is substantially red hot.

3. In the method of manufacturing a source of light for producing a photographic record of light wavel variations corresponding to sound wave variations, the steps consisting in providing an electrode with a coating of an alkaline earth' oxide and activating said coating by heating the electrode to a red heat while in a vacuous space by the passage of an electric current through the electrode, connecting the coated electrode in circuit with the second electrode positioned in said' vacuous space, and passing an alternating current through said circuit until the characteristic spectrum. of vthe coating material comes from the coated electrode.

4. In the method `of manufacturing a source of light for producing a photographic record of llight wave variations corresponding to sound wave variations, the steps consisting in placing two electrodes in a bulb, oneof which electrodes' has a coating of an alkaline earth oxide, evacuating) the bulb,

heating the coatedelectrode by the passage of v an electric current to a red heat, connecting said electrodes in a circuit, and passing a current through said circuit until the characteristic spectrum of the coating materialv comes from the coated electrode. 5. In the method of manufacturing a source of light for producing a photographic lrecord of light Wave variations corresponding to sound Wave variations, the steps consisting in placing two electrodes in a bulb, one of whlch electrodes has a coating of an alkaline earth oxide, evacuating the bulb, heating the coated electrode by the passage of an electric current to a red heat, connecting said electrodes in a circuit while the coated electrode is maintained in a heated condition, and passing a current through said circuit until a glow comes from the coated electrode.

6. In the .method of manufacturing a source of light for producing a photographic record of light wave variations corresponding to sound wave variations, the steps consisting in placing two electrodes in a bulb, one of which electrodes has a coating of an alkaline earth oxide, evacuating 'the bulb, heating the coated electrode by the passage of an electric current to a red heat, connecting said electrodes in a circuit while the coated electrode is maintained ina heated condition, passing a current through said circuit until a glow comes from the coated electrode, and` maintaining the electric current in the circuit between said elec'lrodes until the characteristic spectrum of the coating material comes from the coated electrode.

7. In `the method of manufacturing a source of light producing a photographic record of light wave Ivariations corresponding to sound wave variations, the steps consisting inplacing two electrodes in a bulb, `one of which electrodes has a coating of an alkaline earth oxide, evacuating the bulb, heating the coated electrode by the passage of an electric current to a red heat, connecting said electrodes in a circuit while the coated electrode is maintained in a heated condition, passing a current through said circuit until a glow comes from the coated 115 rent in the circuit between said electrodes until the characteristic spectrum of the coating material comes from the coated electrode and the other electrode is red hot.

8. In the method of manuiacturing a source of light for producing a photographic record of iight wave variations, the steps consisting in placing two electrodes in a bulb, one of which electrodes has a coating of an alka- 125 lline earth oxide, evacuating the bulb, heating the coated electrode to activate the coating, connecting said electrodes in a circuit and passing a current through said circuit until the' characteristic spectrum of the coating 130 j material comes from the coatedelectrode, and

admitting an inert gas to the bulb.

9. In the method of manufacturing a source of light for producing a photographic record of light wave variations, the steps consisting in placing two electrodes in a bulb, one of which Ielectrodes has a coating of an alka line earth oxide, evacuating the bulb, heating thecoated electrode to activate the coating, connecting said electrodes in a circuit and passing a current through said circuit until the characteristic spectrum of the coating material comes from the coated electrode, and admitting helium to the bulb.

10. In the. methode of manufacturing a source of light for producing a photographic record of lightwave variations corresponding to soundwave variations, the steps consisting in providing an electrode with an alkaline earth oxide coating, then heating the time, then connecting'a high voltage source of alternating current between the two electrodes and a lowing alternating current to flow through the tube while a high vacuum is maintained until a green flash is observed between-the electrodes.

In witnessv whereof I have hereunto set my hand this 21st day of May 1927.

THEODORE WILLARD'n CASE.

- electrode to a vred heat while enclosed in a4 highly evacuated space, connecting said coated electrode in circuit with a second electrode positioned in said evacuated space, passing an alternating current through said circuit until the coated electrode 'shows the characteristic spectrum of the coating material, admitting aninert gas to the bulb, and

a barium compound, inserting said electrodo passing a direct current` through the circuit connecting the electrodes. v

11. In the-processv of producing a glow lamp comprising coating anelectrode with an alkaline earth metal, inserting said electrode and a second electrode in a bulb connecting said coated electrode in circuit with a source of directcurrent potential and allowing current to flow for a period of time, then l and a second electrode in a bulb. connecting said coatedelectrode in circuit with a source of direct current potential and allowing current to flow for a period of time, then con-` l necting a high'voltage source of alternating current between the two electrodes and allow-- ing alternating current to iow through the tube while a high vacuum is'maintained until a green flash is observed'between the electrodes. t ,Y I v 13.*In the process of'producing a glow y lamp comprising heating van'electrode in-air oo-an'd applying first a coating of calcium and then a'coating of barium nitrate inserting said electrodes and fa second electrode in a bulb connecting'said coated electrode in cir- A cuit with a source of direct current potential and allowing current to How-.for a peridtof 

